﻿// Copyright (c) Matthias Koch
//
// See the NOTICE file distributed with this work for additional information
// regarding copyright ownership.  rubicon licenses this file to you under 
// the Apache License, Version 2.0 (the "License"); you may not use this 
// file except in compliance with the License.  You may obtain a copy of the 
// License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software 
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the 
// License for the specific language governing permissions and limitations
// under the License.
// 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;

namespace XValidation
{
  public class ValidationInfoProvider : IValidationInfoProvider
  {
    private class Item
    {
      public Item (ICustomAttributeProvider attributeProvider, int argumentIndex, string parameterName)
      {
        AttributeProvider = attributeProvider;
        ArgumentIndex = argumentIndex;
        ParameterName = parameterName;
      }

      public ICustomAttributeProvider AttributeProvider { get; private set; }
      public int ArgumentIndex { get; private set; }
      public string ParameterName { get; private set; }
    }

    public IEnumerable<ValidationItem> GetValidationItems (MethodBase method)
    {
      var items = method.GetParameters()
          .Select ((x, i) => new Item(x, i, x.Name))
          .ToList();

      var methodInfo = method as MethodInfo;
      if (methodInfo != null && methodInfo.ReturnType != typeof (void))
        items.Add (new Item (methodInfo.ReturnTypeCustomAttributes, -1, "return"));

      return items.Select (GetValidationItem)
        .Where (validationItem => validationItem.Validations.Any());
    }

    private ValidationItem GetValidationItem (Item item)
    {
      return new ValidationItem
             {
                 ParameterName = item.ParameterName,
                 ArgumentsIndex = item.ArgumentIndex,
                 Validations = GetValidations (item.AttributeProvider)
             };
    }

    private IEnumerable<IValidation> GetValidations (ICustomAttributeProvider attributeProvider)
    {
      var validations = GetValidationAttributes (attributeProvider).Select (x => x.Validation);
      return validations;
    }

    private IEnumerable<IValidationAttribute> GetValidationAttributes (ICustomAttributeProvider attributeProvider)
    {
      var validationAttributes = attributeProvider.GetCustomAttributes (typeof (IValidationAttribute), true)
          .Cast<IValidationAttribute>();
      return validationAttributes;
    }
  }
}